Prosthetic foot incorporating adjustable bladders

ABSTRACT

A prosthetic foot is characterized by the provision of one or more bladders to vary the performance characteristics of the prosthesis. The bladders preferably include multiple chambers formed by full or partial bifurcation of the bladder, and may be tapered to permit operative alignment of the bladder with certain structural members of the foot. The pressure in the bladder is preferably alterable through the provision of valve means communicating with the bladder. A retaining strap is preferably provided to limit the movement of certain structural members of the foot with respect to other such structural members.

BACKGROUND OF THE INVENTION

This invention relates to prostheses in general, and specifically to theuse of an adjustable bladder in a prosthesis such as a prosthetic foot,which bladder is useful to modify or fine-tune the performancecharacteristics of the prosthesis. In particular, the bladder may bejuxtaposed to various structural members of the prosthesis to "cushion"or otherwise limit or modify the movements thereof.

Although many prosthetic devices have attempted to simulate theambulation of a normal foot, virtually all of them are not readilyadjustable in terms of their performance characteristics. Thisadjustability is especially desirable among amputees who participate ina variety of physical activities requiring varying levels ofenergy-storing and -releasing attributes.

Certainly, some prior art devices more nearly achieve the desired easeof adjustability than do others. For example, see my U.S. Pat. No.4,547,913 for my invention relating to a "Composite Prosthetic Foot andLeg", and U.S. Pat. No. 4,822,363 for my invention relating to a"Modular Composite Prosthetic Foot and Leg". Also, my pendingapplications Ser. Nos. 07/337,374, 07/585,920 and 07/293,824,now U.S.Pat. No. 5,037,444, disclose prosthetic foot devices with similarpreferred materials and methods of manufacture, and with correspondingbenefits therefrom.

Each of my aforementioned inventions is characterized by lightweight,elongated structures incorporating polymer impregnation of superimposedreinforcing laminae maintained in the desired configuration. Suchconfigurations and constructions provide the desirable characteristicsof strength and flexibility in the prosthetic member, and achieve asimulation of the performance of natural feet which had previously notbeen attainable. Such prostheses may be provided in modular assemblies,whereby the particular performance characteristics of a given prosthesismay be adapted and readily adjusted to meet the needs and activity levelof the individual patient.

Notwithstanding the valuable contribution and characteristics of myaforementioned patents and pending applications and specifically themodularity thereof, the adjustment of those prostheses is relativelyinvolved in comparison to that of the present invention. Any adjustmentof the performance characteristics of those prostheses broadly requiresthe disassembly of a covering shroud (if present) and of structuralmembers from each other (through bolt, nut, and washer combinations, forexample). After a new combination of structural members has beenselected, it must similarly be reassembled.

Other prosthetic foot devices are even less readily adjusted, andinclude U.S. Pat. No. 3,335,428 to Gajdos, which attempts to duplicatethe skeletal and skin structure of a natural human foot, U.S. Pat. No.2,075,583 to Lange, which incorporates a rubber form mounted inoperative relationship with a rigid metallic core, and U.S. Pat. No.4,645,509 to Poggi, which teaches a prosthetic foot incorporating amonolithic keel or beam of relatively massive proportions intended toreact to the load of an amputee's body during walking, running, jumping,and the like and to release the resultant stored energy to create footlift and thrust complementing the amputee's natural stride.

Moreover, the dynamic performance of most prior art devices isrelatively stiff and immediate, and cannot approach the gradual"cushioning" achievable with the use of the bladders of the instantinvention in connection with structural members.

Additionally, where bladders have been utilized in prosthetic devices,they have been relatively limited in their performance and usefulness bytheir configuration. For example, U.S. Pat. No. 708,685 discloses apneumatic sole 36, FIG. 2, which interacts with pistons 36 (the number36 was mistakenly used for two different parts in the patent) and 37 andwith a section 35 of the sole 36 to mimic flexure and cushioning of anatural foot. In U.S. Pat. No. 1,151,144 to Wofe et al., an air bag 3(FIG. 4) is filled with air to a desired pressure through a valve 4(FIG. 2). Both of these patents disclose relatively basic uses ofpneumatic devices in prostheses, but include significant shortcomings,such as the apparent likelihood that the wearer may experience a feelingof being "high-centered", especially with respect to lateral stability.

OBJECTS AND ADVANTAGES OF THE INVENTION

It is, therefore, an object of my invention to provide a prosthetic footincorporating bladders which achieve a more gradual dynamic transitionduring loading than possible with prior art devices. The foot preferablyincludes a number of structural members fabricated, for example, frommaterials and methods similar to those disclosed in my above-listedpatents and applications. Such members provide desirable energy-storingand -releasing characteristics and may be readily assembled andconfigured to receive and interact with bladders of the typehereindescribed.

Another object of my invention is to provide a prosthetic foot of theaforementioned character in which the bladder or bladder members arereadily adjustable in pressure, in order to permit a corresponding readyadjustment of the feel and performance of the prosthesis experienced bythe wearer.

Moreover, the preferred embodiment of the bladder of my invention may befabricated in a variety of configurations, including those havingmultiple chambers and tapered cross-sections. Such configurations permitthe bladder or bladders to be positioned in unusual but useful locationswithin the prosthesis and the structural members thereof, and provideadditional benefits such as a lessened feeling of being "high-centered",as described above.

It is a further object of my invention to provide a bladder useful inprosthetic devices such as a prosthetic foot of the aforementionedcharacter. In a preferred embodiment, and as indicated above, thebladder includes means for adjusting the internal pressure and thecorresponding feel and performance characteristics of the bladder andthe prosthesis into which it is incorporated.

The prosthetic device of the invention, including the structural membersand the bladders, is preferably of modular configuration, resulting inready assembly and adjustability thereof, similar to my aforementionedinventions. The various components of the foot of my inventionpreferably can be readily exchanged with correspondingly-constructedcomponents, or even differently-constructed components, to provide sizeand performance adjustments and adjustability to suit the size of footof the amputee or the stride, height, weight, and activity level of theamputee. Therefore, a range of combinations of spring rate,adjustability and size can be provided to the amputee, achieving anatural stride and resilience of gait, which has not been fullyobtainable by prior art prosthetic devices.

Consequently, the foot of my invention is characterized by extreme lightweight, instantaneous response to imposed loads and correspondinglyinstantaneous delivery of stored energy when the gait of the wearerindicates that such stored energy is to be released. The wearer of thefoot may engage in a wide variety of activities and may easily andprecisely adjust the stiffness and spring characteristics according tothe particular activity.

Other objects and advantages of the invention will be apparent from thefollowing specification and the accompanying drawings, which are for thepurpose of illustration only.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a side elevation view of a prosthesis constructed inaccordance with the teachings of the invention and incorporating asingle bladder member;

FIG. 2 is a side elevation view of an alternative embodiment of aprosthesis constructed in accordance with the teachings of theinvention, and is similar to FIG. 1 but includes an additional bladdermember and means for adjustment of the internal pressure of thebladders;

FIG. 3 is a plan view, taken along line 3--3 of FIG. 2;

FIG. 4 is an isometric view of an adjustable bladder means constructedin accordance with the teachings of the invention;

FIG. 5 is a sectional side elevation view, taken along line 5--5 of FIG.4;

FIG. 6 is an isometric view of an alternative embodiment of anadjustable bladder means constructed in accordance with the teachings ofthe invention; and

FIG. 7 is a sectional side elevation view, taken along line 7--7 of FIG.6.

DESCRIPTION OF PREFERRED EMBODIMENT

Referring to the drawings, and particularly to FIG. 1 thereof, I show afoot prosthesis 10 constructed in accordance with the teachings of theinvention and including structural members 12 and bladder means 14 suchas a bladder member 16 operably assembled therewith. A shoe 18 is shownin phantom as it might be worn with the prosthesis.

As indicated above, the structural members 12 may be fabricated,combined and assembled in a wide variety of shapes, sizes, andperformance characteristics, and are preferably constructed frommaterials and methods described in my previously mentioned patents andpending applications. For purposes of illustration, FIG. 1 disclosesstructural members including a heel portion 20, a forefoot portion 22,and an auxiliary member 24.

In the preferred embodiment, the forefoot portion 22 and the auxiliarymember 24 are operatively attached to a pylon 26 through the use of nutand bolt combinations 28 or similar expedient, or are otherwise adaptedfor operative disposition on a wearer's stump. The heel portion 20 isoperatively (and preferably demountably) connected to the forefootportion 22 through the utilization of nut and bolt combinations 30 orthe like.

The bladder means 14 such as bladder member 16 is preferably fabricatedfrom a suitably strong, flexible, leak-proof, lightweight material suchas urethane or the like. By way of example, FIGS. 4 and 5, the bladdermay be formed by heat sealing appropriately sized and shaped pieces ofmaterial 32 and 34 to each other. Suitable thicknesses of urethane havebeen found to be 0.01 to 0.02 inches, but a wide range of thicknessesand materials may be utilized with efficacy. Bladder pressures of up to80 psi have been utilized with efficacy.

The bladder means 14 is preferably enwrapped in covering means 36fabricated of Kevlar or similarly strong material to prevent the bladdermeans 14 from exploding under high pressures and to help define thefinal inflated shape of the bladder means 14. In preferred embodiments,FIGS. 2, 4-7, covering means 36 includes sections 38 and 40, which maybe stitched together (as indicated at 42) at the perimeter of thebladder member 16, before or after the sections 38 and 40 have been cutto their desired final shapes. Those skilled in the art will understandthat a variety of covering materials and methods of fabrication andassembly thereof may be utilized with efficacy, without departing fromthe teachings of my invention.

Bladder means 14 is preferably encloses air, CO₂, or a similar gas-likesubstance, but may alternatively enclose liquids or gels such as water,silicone, or the like. Any such assembly may provide the desireddeformability and consequent "cushioning" or energy-storing, absorptionand release.

To provide ready adjustment of the spring rate and performance of theprosthesis to the wearer, bladder means 14 preferably includesadjustment means 44 such as a PVC or urethane tube 46 which issolvent-bonded or otherwise suitably attached to the bladder member 16(such as at 48) so as to be in fluid or gaseous communication with theinterior of the bladder.

Adjustment means 44 further preferably includes appropriate valve means50 on the opposite end of the tubing 46. In the preferred embodiment,the valve 50 is adapted to receive a needle from an air pump (not shown)or from a CO₂ cartridge (not shown), as more thoroughly describedherein, and may be disposed on a suitable bracket 52, FIGS. 2 and 3, forready accessibility to the wearer. The valve member may be operativelyconnected to the tubing 46 by expanding the end of the tubing andinserting the valve therein, as at 54, or through the provision of anadaptor 56.

If indicated, passageways such as holes 58, FIG. 2, may be provided inthe structural members 12 to accommodate the tubing 46. The passageways58 are preferably of a size and are positioned to facilitate assemblyand ambulation of the prosthesis without binding or damaging the tubing46.

An alternative embodiment 60 of the bladder means 14 is illustrated inFIGS. 6 and 7, and is fabricated and operated in a manner similar tothat described above, but is bifurcated or otherwise divided to includechambers 62 and 64. This bifurcation may be readily achieved byheat-sealing a strip 66 across all (not shown) or a portion of thebladder 60, or may be fabricated in numerous other manners. Suchconstructions may include a wide variety of shapes (such as the modifiedU-shape of FIG. 6) and any beneficial number of chambers, which chambersmay or may not be in gaseous or fluid communication with one another,depending on the desired performance of the bladder.

The provision of the heat-sealed strip 66 in the bladder 60 provides anumber of benefits to the wearer of the prosthesis. For example, thestrip 66 may be utilized to cause a tapering or reduction incross-section along the length of the bladder means 14, as bestillustrated in FIG. 7. A tapered bladder may be more readily disposed incertain locations in the prosthesis 10 than is a non-tapering bladder,such as under a structural heel member 68, FIG. 2. Such a bladder mayalso provide more desirable or more gradual cushioning effects than anon-tapering bladder.

Additionally, the provision of multiple chambers such as chambers 62 and64 reduces and even eliminates the above-described problem of feeling"high-centered". Instead of providing only a central contact locationbetween the bladder member 60 and the overlying heel member 68, FIG. 2,the chambers 62 and 64 provide multiple contact surfaces and disposesuch areas of contact laterally from the center of the heel member 68.

Another beneficial modification to my invention is the provision of arestraining or retaining means such as a strap 70, FIG. 1. The strap 70is fabricated from a suitably tough, flexible material such asimpregnated canvas or the like, and is configured and assembled with thestructural members 12 and/or the bladder means 14 to achieve desiredstress-storage and -release performance in the prosthesis.

For example, the strap 70 may be operatively attached to the forefootportion 22 through the aforesaid assembly 30 of nuts and bolts, and maybe releasably attached around the auxiliary structural member 24 throughthe provision of Velcro®-type fasteners or similar expedient.

The strap 70 provides a number of benefits. For example, if juxtaposedto a bladder member 16, the strap may be appropriately tightened to"flatten" the bladder, thus increasing the contact areas between thestructural members and the bladder, and possibly reducing the"high-centered" problem discussed above.

Moreover, restraining means such as the strap 70 may be incorporated atvarious locations on the prosthesis 10 to restrict the distance thatassociated structural members 12 may move from one another. Theretaining means may be utilized to prevent undesirable excessive loadingand stressing of a particular member 12, and to combine thespring-stress response characteristics of the associated structuralmembers 12 under certain loading conditions. For example, the strap 70as assembled in FIG. 1 permits the auxiliary member 24 to assist inraising the toe of the prosthesis 10 and to store and release springenergy when the heel portion 20 is struck on the ground in front of thewearer.

In operation, the bladders may be completely deflated if the wearerdesires the performance characteristics of the structural members. Forexample, in the assembly illustrated in FIG. 3, the forward bladdermeans 14 would be non-functional if deflated, and the spring-stressresponse of the auxiliary member 24 would be combined with that of theforefoot portion 22 only after the forefoot portion was sufficientlydeflected to contact the auxiliary member 24.

As the bladder is inflated to increasing pressures and volumes, however,the combination of the spring-stress responses of the forefoot portion22 and the auxiliary member 24 effectively occurs after correspondinglyless and less deflection of the forefoot portion. If the bladder memberis sufficiently inflated, the forefoot portion 22 and the auxiliarymember 24 would always act and react in unison.

Additionally, the above-indicated cushioning effect of the bladder means14 can be dependent upon the degree to which the bladder is inflated.Although the bladder will preferably always retain some amount ofcompressibility and "cushioning", the compressibility could approach anegligible amount if the bladder is sufficiently inflated, therebyvirtually eliminating any cushioning effect during ambulation of theprosthesis 10.

Those skilled in the art will understand that the bladder means of myinvention may be utilized with efficacy in a wide variety of prostheticdevices, including prosthetic feet of substantially differentconfigurations than those disclosed in the drawings.

It will be obvious to those skilled in the art that an extremely widevariety of performance characteristics may be achieved through theincorporation of the bladder means of my invention into any givenassembly of structural prosthetic members. Moreover, the selection ofand adjustment to a desired set of performance characteristics may bereadily achieved by the wearer of the prosthesis without the need fordisassembly and reassembly of various components. The wearer mayrepeatedly adjust the spring-stress response characteristics of the footwith very little time or effort required. The valve means 50 includes ableed function to release pressure in the bladder and, as explainedabove, permits ready inflation of the bladder through the use of a handpump, a CO₂ cartridge or the like.

For example, if an individual partakes in sports or other activitieswhich subject the prosthesis 10 to greater loads than those of normaldaily wear, the bladder members 16 may be appropriately inflated priorto the periods of greater activity, and deflated thereafter.

The prosthesis and bladder means of my invention has been described withsome particularity but the specific designs and constructions disclosedare not to be taken as delimiting of the invention in that variousmodifications will at once make themselves apparent to those of ordinaryskill in the art, all of which will not depart from the essence of theinvention and all such changes and modifications are intended to beencompassed within the appended claims.

I claim:
 1. In a prosthetic foot, the combination of: attachment meansto facilitate operative engagement of the foot with a wearer's stump; aplurality of elongated, non-inflatable, curvilinear structural membersoperatively attached to said attachment means and/or to each other, saidstructural members providing substantial energy storage and returnduring ambulation; and bladder means adjacent said structural members,whereby said bladder means cooperate with said structural members indetermining the energy-storage characteristics of said foot, said footconstituting means for substantially operable ambulation without regardto the presence or pressure of said bladder means.
 2. The prostheticfoot of claim 1, in which at least one of said bladder means is providedwith a plurality of chambers.
 3. The prosthetic foot of claim 1, inwhich at least one of said bladder means is formed in a modifiedU-shaped configuration.
 4. The prosthetic foot of claim 1, in which atleast one of said bladder means includes a partial bifurcation whichdivides said bladder means into a plurality of sections while retainingfluid communication between said sections.
 5. The prosthetic foot ofclaim 1, in which said bladder means includes a heel bladder operativelydisposed beneath a lower, rearwardly disposed structural member.
 6. Theprosthetic foot of claim 1, in which said bladder means is covered witha protective material.
 7. The prosthetic foot of claim 1 or claim 2 orclaim 3 or claim 4 or claim 5 or claim 6, including retaining meansjuxtaposed to a plurality of said structural members to restrict themovement of said members in relation to one another.
 8. The prostheticfoot of claim 1 or claim 2 or claim 3 or claim 4 or claim 5 or claim 6,including adjustment means operatively associated with said bladdermeans to facilitate adjustment of the pressure or volume of said bladdermeans.
 9. The prosthetic foot of claim 1 or claim 2 or claim 3 or claim4 or claim 5 or claim 6, in which said bladder means contains a gaseoussubstance.